在51个数中,所有3的倍数,17的倍数都要除去,都能约分3/51 6/51 9/51 12/51 15/51 18/51 21/51 24/51 27/51 30/51 33/51 36/51 39/51 42/51 45/51 48/5151/51 还有17/51 34/51 除外,总共真分数有51-19=32个...